A study of bending deformations in carbon nanotubes using the objective molecular dynamics method.

Abstract

Bending of carbon nanotubes is a topic which has applications in several areas of nanotechnology, including nanotoxicology and NEMS. Atomistic simulations are necessary to understand in detail the fundamentals and the phenomena observed in experiments. Objective molecular dynamics allows the imposition of angular boundary conditions on atomistic systems. Coupled with the Tersoff potential, objective MD is used to systematically investigate reversible elastic bending in carbon nanotubes up to 4:2 nm in diameter. A contrasting behavior is revealed. Single-wall tubes buckle in a gradual way, with a clear intermediate regime before they fully buckle and significant hysteresis between bending and unbending cycles, in agreement with previous studies. Multi-walled tubes with closed cores, not commonly studied using direct atomistic methods, exhibit a hysteresis-free, rate- and size-independent direct transition to an unusual wavelike mode with a 1 nm characteristic length. This rippling mode has a nearly-linear bending response and causes a #24; 35% reduction in the stiffiness of the thickest multi-walled tubes.